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Whats is a double action hammer mechanism in a pistol?

Discussion in 'General Gun Discussions' started by AsianDragonPower, Aug 25, 2006.

  1. ?????????

    anyone know
  2. SMLE

    SMLE Well-Known Member

    The differance between single and double action has more to do with the trigger than the hammer. On the old West type revolvers such as the Colt, the hammer had to be manually cocked, then the trigger performed the "single action" of releasing it. Double action revolvers do not have to be cocked first, the trigger performs the "double action" of cocking and releasing. The terms are the same with semi-auto pistols as well. The Colt 1911 has to be cocked before the first shot can be fired. This is normally done when loading. The Beretta 92 however is double action, so you just pull the trigger. The Beretta and similar "DA" autos have a "de-cocking" lever that lowers the hammer safely without firing so that the pistol can be carried with the hammer down and a round loaded in the chamber. The 1911, Browning High Power and other "SA" autos have manual safties that lock the trigger sear so that the pistol can be carried with the hammer cocked and a round loaded. Pistol like the Glock are not really either SA or DA.

    Hope this helps.
  3. gunsmith

    gunsmith member

  4. gunsmith

    gunsmith member

    you know...

    @ over 3 thou post you'd think I'd know all this...there is so much I don't know.
  5. OOOOOOOOOOOOOOOOOOoooooooh thx:)

    wikipedia can be edited by anyone to that one guy
  6. El Tejon

    El Tejon Well-Known Member

    Think of it this way, Asian:

    single action: the weapon can be fired one way

    double action: the weapon can be fired two ways


    Get to the range with a buddy and he'll show you what I mean and you get to shoot.:D
  7. Bullseye57

    Bullseye57 Bullseye

    A double action trigger is one when the trigger is depressed by the operator, the hammer moves in two directions with one stroke of the trigger. First the hammer moves rearwards then releases forwards to fire the cartridge. You can see a double action trigger at work here; http://science.howstuffworks.com/machine-gun.htm Scroll halfway down the page to the revolver. Roll your pointer over on to the trigger and click the left mouse button,

    In a single action pistol, the hammer only moves in one direction when the trigger is depressed. In order to do this, the hammer must be manually cocked, either by the operator or by mechanical action of the pistol.

    Hope this helps.

  8. unspellable

    unspellable Well-Known Member

    Single action: 1 mode of operation.

    Manually cock the hammer, pull trigger.

    Double action: 2 modes of operation.

    Manually cock the hammer, pull trigger OR pull tigger and the trigger cocks and releases the hammer. (self cocking mode)

    Triple action: 3 modes of operation.

    Both of the above plus manually cock the hammer and push it down for hammer down carry while actually cocked. Pulling the trigger raises the hammer (But does not cock it, it's already cocked.) and releases it.

    The term "double action only" as used when referring to a self cocking only action is an oxymoron that leads to confusion since the term actually implies TWO modes of operation.

    There is another type of action that I've not heard a good term for. The Glock is an example. In this type of action cycling the slide brings the action to half cock, pulling the trigger completes cocking and releases the striker. (No hammer) With appropriate mechanical leverage completing the half cock takes less trigger pull force than a full self cock.

    There are a few obscure types out there that you are unlikley to encounter such as the lemon squeezer which lies in the realm of the collector.
  9. CNYCacher

    CNYCacher Well-Known Member

    It get's real confusing when you get into auto-loading pistols instead of revolvers. Took me forever to figure it out, especially when you have DAO thrown into the mix.

    On top of what everyone else has already stated, one significant difference between double-action and single-action is the trigger is usually easier to pull on a single-action, because the hammer is already cocked. On a double-action, you are cocking the hammer as you are pulling the trigger, so it's harder to pull. Double-action allows you to fire in single-action mode, by cocking the hammer first, just like a single-action.

    For autoloaders: it get's wierd:

    All auto-loaders eject the old round and load a new round when the slide goes back.
    The slide will go back when a round is fired, or you can pull it back manually, this is called "racking" the slide. One example of a time when you want to rack the slide is to load a round from the magazine if there is not one already loaded.
    Single and double-action autoloaders have a hammer that is cocked when the slide goes back.
    If the hammer is not cocked on a single-action, it will need to be cocked before the trigger will do anything, either by racking the slide, or by manually cocking it.
    A double-action auto-loader will cock the hammer for you the first time you pull the trigger, each shot after that the hammer will be ready because the previous shot sent the slide back, cocking the hammer and loading a new round.
    Here is the confusing part:
    Double-action-only (DAO) auto-loaders are not cocked by the slide, nor can you cock them manually. Each time you pull the trigger, you are cocking and releasing the hammer. This makes for a harder trigger pull each time. Actually, there isn't really a "hammer" to speak of (or see), it's a different mechanism in this case.

    Yes it can, have you ever tried it? Try posting some nonsense on that page linked above, then hold your breath until someone corrects it. You won't even pass out.
  10. Jim K

    Jim K Well-Known Member

    I guess this is redundant, but

    Single action - trigger pull (1) releases hammer/striker to fire the gun (the hammer has to be cocked manually or by some force other than the trigger).

    Double action - trigger pull (1) cocks the hammer/striker, then (2) releases it to fire the gun.

  11. Lupinus

    Lupinus Well-Known Member

    it isn't the hammer, it is the trigger. You have three basic types of trigger, SAO(single action only) DAO(double action only) and DA/SA

    In a single action pulling the trigger releases the hammer, striker, or firing pin and that is all it does. The triggers only job in the gun is holding the hammer and then releasing it. The action is cocked by other means, either manualy by the user in one of the various ways or by the slide of a pistol such is in an auto pistol.

    A double action trigger however both moves back the hammer/striker/pin and then releases it. That is why they have heavier and longer trigger pulls, they are doing more work.

    Also there are DA/SA pistols which do both. The first pull is double action and following shots are single action.

    Also some guns can be used either way, such as the case of many touble action revolvers you can either use the trigger or manualy cock the hammer for a much shorter lighter trigger pull.
  12. bender

    bender Well-Known Member

    yeah, me too. I've collected guns for around 20 years, and have always known the diff between SA & DA revolvers, but never paid attention to what it meant on a semi-auto pistol. I always thought the slide had to be racked back before the first shot on any semi-auto :(
    I learn something every day here...:eek:
  13. El Tejon

    El Tejon Well-Known Member

    DAO=single action.:)
  14. haole_boySS

    haole_boySS Well-Known Member

    You always thought correct. If you don't rack the slide on a semi-auto handgun you will not have a round in the chamber. (this assuming of course that you inserted a loaded magazine)
    IE: On the Beretta 92F/96F (a well known DA/SA pistol) you can insert a loaded magazine and pull the DA trigger till you are blue in the face and not fire a single shot....unless you rack the slide first, thus loading the chamber.

    I had to explain the whole SA, DA/SA, DAO to my father last night. He was slightly confused. The only pistol he has is a .357 Colt Python. That turned out to be the easiest way to explain the DA/SA action of a semi-auto....just compare it to his revolver.

    Hope this helps someone.


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